The present invention relates generally to a rotary cutting device and more particularly a device for the cutting of windows, notches, orifices or other patterns in relatively thin, flexible sheet-like material in either sheet or web form.
Many envelopes have a transparent panel or window for allowing visual inspection of the enclosure. These window envelopes are manufactured from a web of paper material which is initially cut into blanks having a predetermined shape. A panel is subsequently cut from the blank by a panel cutting apparatus to form the window. Thereafter, the blank is then folded, gummed, printed and packaged to form the finished envelope.
U.S. Pat. No. 4,823,659 to Falasconi describes a conventional rotary panel cutting apparatus comprising a cutting tool in the form of a cutting plate or die and a rotary die holder which brings the cutting die into successive contact with the envelope blanks which advance on a conveyor system. The cutting die has a raised cutting edge which is adapted to engage the blank and cut the panel. The die holder, sometimes called a die cylinder or drum, is mounted for rotation on a drive shaft synchronized with the conveyor system so that the cutting die engages a different envelope blank for each rotation of the die holder.
The surface of the die holder has a plurality of transport and vacuum orifices which communicate with corresponding air chambers which, in turn, selectively communicate with a source of vacuum or compressed air. The transport orifices are adapted to engage the envelope blank and, when the vacuum source is activated, carry the blank adjacent to the surface of the die holder. The rotation of the die holder carries the envelope to a cutting station where the blank is passed between the cutting die and a cutting bar so as to cut the panel in the envelope blank. The vacuum orifices are disposed within the periphery of the dies"" cutting edges and, when the vacuum source is activated, form a localized vacuum zone within the vicinity of the cutting die to retain and carry away the panel which is cut from the envelope blanks. The envelope blank and the cut panel may be released from the die holder and the cutting die, respectively, by terminating the vacuum source or applying the compressed air to the transport and vacuum orifices. The vacuum and compressed air supply to each opening is controlled by means of valves or attachment tubes which are manually attached to each individual orifice. The attachment tubes typically rotate in unison with the die holder.
Unfortunately, the prior art panel cutting apparatuses suffer from numerous drawbacks. Since the die holder typically rotates from zero to about 1500 rpm, it is extremely difficult to obtain a proper seal between the rotating vacuum tubes and the feed tubes which permits the envelope blank to move, resulting in improper alignment between the cutting die and the envelope blank. Similarly, it is extremely difficult to obtain a proper seal at the vacuum orifices between the die holder and the drive shaft due to wear and abrasion, resulting in insufficient vacuum to carry the envelope blank and the panel and jamming of the cutting apparatus. It is also difficult to apply the vacuum or air at the correct time during the rotation of the die holder.
Methods used to retain the cutting die adjacent to the die holder including mechanical clamp assemblies and magnetic clamp assemblies suffer several disadvantages. The mechanical clamp assemblies, which clamp one or both of the leading and trailing ends of the cutting die, are relatively complicated devices which are time consuming to assemble and disassemble and expensive and difficult to manufacture.
Another drawback is the lack of adjustability of the apparatus to cut out panels of different sizes as well as different locations on the blank. Attempts to provide an adjustable die holder capable of receiving different size cutting dies have been unsuccessful because the holding mechanisms, such as removable cover plates and holding keys, used to attach the cutting dies to the die holders leave significant areas without the vacuum orifices necessary to carry the envelope blank and the panel. In addition, these attempts have resulted in die holders which become unbalanced during rotation.
In order to minimize the assembly and disassembly downtime, magnetic clamp assemblies, having magnetic strips disposed in the surface of the die holder to magnetically attract and hold the cutting die, have been used. Unfortunately, the forces resulting from the rotation of the die holder may cause the cutting die to slide laterally on the surface of the magnets. To prevent the lateral movement of the cutting die, magnetic die holders have also utilized cumbersome mechanical clamping assemblies to hold at least the leading end of the cutting die while the magnetic clamps hold the remaining portion of the cutting die. Attempts to prevent lateral movement by increasing the magnetic force and maximizing the number of magnetic strips disposed in the die holder surface have resulted in minimizing the number of the vacuum orifices available for retaining the envelope blank and the panel.
Accordingly, it is an object of the invention is to provide an improved cutting tool for cutting panels from blanks of sheet-like material.
It is an object of the invention to provide a cutting tool having an improved air delivery system.
It is a more specific object of the invention to provide an improved air delivery system which efficiently delivers vacuum to the die holder with minimal leakage.
It is another object of the invention to provide a die holder which minimizes air leakage due to wear or abrasion.
Another object of the invention is to provide an improved die holder for a panel cutting tool.
Still another object of the invention is to provide a die holder which maximizes the vacuum openings disposed along its outer surface. A related object is to provide a cover plate and a holding key which is capable of retaining the envelope blank and the panel during the cutting operation.
It is an object of the invention to provide a die holder which functions in an efficient manner, is easily assembled and is adapted for operation with different size cutting dies.
It is a related object of the invention to provide a die holder which may be easily and readily adjusted to position the cutting die.
It is an object of the invention to provide a die holder having a more equal weight distribution.
It is an object of the invention to provide a die holder which may be easily removed from the die shaft.
It is an object of the invention to provide an improved magnetic cutting tool for cutting patterns from blanks of sheet-like material.
It is an object of the invention to provide a cutting tool having an improved distribution of magnets and air orifices.
A more specific object of the invention is to provide a magnetic cutting tool which minimizes the number of magnetic strips while maximizing the number of vacuum orifices disposed over the die holder surface.
Another object of the invention is to provide a magnetic die holder which prevents the cutting die from moving laterally on the die holder surface.
A rotary cutting assembly is provided for cutting a panel from an envelope blank or the like. The cutting assembly comprises a cutting die mounted on a die holder adapted to be mounted on a drive shaft for rotating about an axis. The die holder has a plurality of surface orifices radially communicating with corresponding longitudinally directed feed tubes for supplying vacuum or air to the surface and into the vicinity of the envelope blank.
In accordance with one aspect of the invention, a novel air delivery assembly is provided for delivering vacuum and/or air to the die holder. The air delivery assembly comprises a stationary plate disposed at least at one end of the die holder and defining a groove member for selectively supplying vacuum and/or air so that a supply of vacuum or air is selectively supplied at the surface orifices of the die holder when rotation of the die holder aligns the longitudinal feed tubes with the groove member.
In one embodiment, the air delivery assembly comprises a transport assembly and a vacuum assembly disposed on opposing sides of the die holder. The transport assembly is adapted to feed vacuum to the die holder in order to retain the envelope blank adjacent to the die holder and xe2x80x9ctransportxe2x80x9d the envelope blank as the holder rotates through the cutting operation. The vacuum assembly, in turn, is adapted to feed vacuum to the die holder in order to retain the panel cut from the envelope blank adjacent to the die holder until a predetermined position is reached wherein the panel is released from the die holder. At predetermined positions, the transport and vacuum assemblies may feed compressed air to the die holder in order to release the envelope blank and the panel, respectively.
In accordance with certain objects of the invention, the die holder has at least one groove for receiving a holding key which cooperate to clamp one of the edges of the cutting die therebetween for securing the cutting die to the holder. In one embodiment, the holding key may have a plurality of orifices for supplying vacuum or air to the surface of the key and at least one longitudinally directed feed tube which radially communicates with the orifices for supplying vacuum and/or air to the orifices. In another embodiment, a transport key is provided which is adapted to engage and retain the leading edge of the envelope blank adjacent to the outer surface of the key as the die holder rotates. A feeder key is also provided which is adapted to engage and retain the envelope blank or the panel cut from the blank adjacent to the outer surface of the key as the die holder rotates.
In accordance with certain objects of the invention, the die holder may have a removable cover plate having a plurality of orifices disposed on the plate surface and feed tubes subjacent the plate surface which communicate with the orifices for supplying vacuum or air to the orifices. In one embodiment, the feed tube extends in the longitudinal direction so as to communicate with both ends of the cover plate. In another embodiment, the feed tube only communicates with one end.
The operator may select whether individual feed tubes (and the corresponding orifices) communicate with either the transport assembly or the vacuum assembly. In applications where the envelope blank is adjacent to the certain predetermined orifices and it is desired to retain the envelope blank adjacent the die holder, the feed tubes corresponding to the predetermined orifices communicate with the transport assembly. Conversely, if the panel is adjacent to the predetermined orifices, the feed tubes corresponding to the predetermined orifices communicate with the vacuum assembly.
In accordance with certain objects of the invention, the die holder may have an outer surface having a slot extending along the longitudinal axis for detachably receiving the leading end of the cutting die and a plurality of magnetic members disposed in the die holder surface for attracting the cutting die. In a preferred embodiment, the die holder may have a plurality of orifices disposed between adjacent magnetic members for delivering vacuum or air to the die holder surface. In order to maximize the number of orifices while minimizing the number of magnetic members, it is preferred that the magnetic members be disposed in a plurality of rows wherein each row contains alternating magnets and orifices and a row of orifices are disposed between each adjacent row of magnets.
These and other features and advantages of the invention will be more readily apparent upon reading the following description of a preferred exemplified embodiment of the invention and upon reference to the accompanying drawings wherein: